The first stable build of Ruby 1.9.1 has been released. Ruby 1.9 represents some significant changes over 1.8, including internationalization support, many syntactic changes to the language, and new features such as fibers.

This release also has significant impact on alternative implementations of Ruby as well. As Charles Nutter noted in the thread following the release announcement:

Congratulations! Now that the stable release is out, we will pull 1.9.1 stdlib into JRuby. We'll ship our 1.9.1-compatible (mostly? hopefully?) release of JRuby 1.2 in late February.

The release packages can be downloaded (files "ruby-1.9.1-p0.*") from the ftp directory here. (Note these packages are not pre-built binaries but source drops that require the appropriate C++ compiler.)

Update: the binary distribution of Ruby-1.9.1 has hit the official download page.